Venting water-tight battery-operated devices

ABSTRACT

Water-tight battery powered appliances, for example personal care appliances such as razors and toothbrushes, are provided. The appliances include a housing having a seal that allows gases, e.g., hydrogen, to vent from the appliance without allowing water to enter.

TECHNICAL FIELD

This invention relates to venting a gas, e.g., hydrogen, from theinterior of water-tight battery-operated devices, such as smallappliances for personal care use.

BACKGROUND

Under certain conditions, hydrogen can accumulate in the interior ofbattery-powered appliances. The hydrogen may be released from thebattery, or may be created by electrolysis outside the battery. Mixingof this hydrogen with ambient oxygen can form an explosive gas, whichcould potentially be ignited by a spark from the motor or switch of thedevice.

This problem has been addressed in various ways. In appliances anddevices that do not need to be water-tight, the housing of the devicewill often contain an opening through which gases can vent.

In the case of devices that are operated in wet environments, forexample electric toothbrushes and battery powered razors, the openingmay be covered by a microporous membrane. The membrane is permeable tohydrogen gas, but impermeable to water. While this approach is generallyeffective in venting hydrogen from the interior of the device, the useof a membrane tends to be expensive and to increase the complexity ofthe product assembly process.

Another approach involves reacting the hydrogen gas rather than ventingit. In this case, a hydrogenation catalyst is provided within the deviceto cause the hydrogen gas to react with oxygen and form water, and asilica dessicant is provided to absorb the water. Water-tight camerasutilizing this approach are described in U.S. 2002/0045093.

SUMMARY

In general, the present invention features battery-powered devices inwhich venting of gases (e.g., hydrogen) is provided through an aperturethat is sealed by a seal that is normally closed and remains closed whenpressure is applied from outside of the device, but opens when apredetermined internal pressure is exceeded. In some cases, the openingin the device housing that is sealed is an opening that serves anotherpurpose in the device, e.g., an opening through which an actuatorextends.

In one aspect, the invention features a water-tight, battery poweredappliance including (a) a housing, having a generally hollow interiorand an aperture through which gas can be vented from the interior; and(b) a seal, positioned to normally cover the aperture, the seal beingconfigured to flex in response to pressure within the hollow interiorand move away from the aperture when a predetermined pressure, forexample about 0.1 to 2 bar, is exceeded.

The appliance may be a personal care appliance, such as a razor ortoothbrush. Thus, the appliance may further include a razor cartridge ortoothbrush head mounted on the housing.

The functionality of the appliance may be turned on and off using anactuator. The actuator may in some cases extend from the aperture. Insuch cases, the seal may surround a stem portion of the actuator.

In some instances, the seal includes an elastomeric member, for examplea bellows-type seal or a ring-shaped elastomeric gasket. The aperturemay be positioned within a circumferential groove in an outer surface ofthe housing, and the seal may include a ring-shaped element, e.g., anelastomeric gasket, positioned in the groove to cover the aperture. Thering-shaped element may be pre-stressed to hold the ring-shaped elementtaut against the outer surface of the housing.

In another aspect, the invention features a water-tight, battery poweredappliance including (a) a housing, having a generally hollow interiordefining an inner wall, the housing having an aperture through which gascan be vented; (b) a carrier, disposed within the housing and configuredto hold a battery, the carrier having an aperture through which gas canbe vented; (c) a first seal, positioned between the carrier and theinner wall of the housing, allowing fluid communication between theaperture in the housing and the aperture in the carrier, but sealingagainst passage of fluid past the first seal into the housing; and (d) asecond seal, positioned to normally cover the aperture in the carrier,the seal being configured to flex in response to pressure within thehollow interior and move away from the aperture when a predeterminedpressure is exceeded.

In some cases, the first and second seals each comprise an elastomericmember. The housing and carrier may both be generally cylindrical, inwhich case the first seal may include a pair of ring-shaped gaskets,positioned one on each side of the apertures in the carrier and housingto isolate the apertures from the rest of the housing.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features andadvantages of the invention will be apparent from the description anddrawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a partial axial cross-sectional view of an appliance accordingto one embodiment of the invention. FIG. 1A is a radial cross-sectionalview taken along line A-A in FIG. 1. FIG. 1B is an enlargedcross-sectional view of the sealing member used in the appliance of FIG.1.

FIG. 2 is a diagrammatic view of a portion of an appliance according toanother embodiment of the invention. FIG. 2A is a radial cross-sectionalview taken along line A-A in FIG. 2. FIG. 2B is an enlarged diagrammaticview of the upper portion of FIG. 2, illustrating the gas flow path inthis embodiment.

FIG. 3 is a diagrammatic view of a portion of an appliance according toa further embodiment of the invention. FIG. 3A is an enlarged detailview of area A in FIG. 3.

FIG. 4 is a diagrammatic view of a portion of an appliance according toyet another embodiment of the invention. FIG. 4A is an enlargeddiagrammatic view of the lower portion of FIG. 4, illustrating the gasflow path in this embodiment.

DETAILED DESCRIPTION

Referring to FIGS. 1-1A, an appliance 10, for example a razor ortoothbrush, includes a generally cylindrical handle housing 12. Abattery (not shown) is disposed within the housing when the appliance isused, resulting in the possible generation of hydrogen gas. The housing12 is sealed in a water-tight fashion. An actuator button 14 is exposedat the outer surface 16 of the housing, allowing a user to depress thebutton to activate the functionality of the device, for example thebrushing function of a power toothbrush head, or a vibrating function ofa battery-powered razor for wet shaving. The actuator button extendsfrom a stem 18. Stem 18 is press-fit into a sleeve 20 which slides downwhen the button is depressed, activating the functionality of the device(how this occurs will not be discussed, as it is not relevant and willdiffer from device to device). The actuator button is returned to itsnormal, non-depressed position by a return spring 22.

The opening around the sleeve 20 and the adjacent wall 24 of flange 25of the housing 12 must be sealed in order for the device to becompletely water-tight. Sealing is provided by a bellows seal 26 havingan upper sealing ring 28, a lower sealing ring 30, and an outwardlybowed bellow 32. Upper sealing ring 28 seals against the intersection ofthe lower surface of the button with the upper end of the stem, whilelower sealing ring 30 seals against the outer surface of flange 25.Under normal interior pressure conditions, the bellow 32 resilientlybiases the sealing rings against the surfaces they seal against.Preferably, bellows seal 26 is an elastomeric seal that is pre-stressedinto its sealing configuration by stretching it over the flange 25.

When a predetermined interior pressure within the housing is exceeded,e.g., 0.1 to 2 bar, indicating the presence of hydrogen gas, the bellowsseal flexes, temporarily breaking the seal at the upper and/or lowersealing ring (generally at the lower sealing ring) and allowing the gasto vent from the device. Normally, the path of gas is through a gapbetween the sleeve 20 and the flange 25, into the chamber defined by theinner wall of the bellow 32, and then, as the seal is broken, past thelower sealing ring and through a gap between the button 14 and thehousing 12.

As soon as pressure within the housing normalizes, the bellows sealreturns to its normal, unflexed position in which it renders the devicewater-tight. Because the seal is only broken for a very short time andto a very small extent, and because the interior pressure is higher thanthe external pressure, it is unlikely that any water will penetrate intothe device during venting.

The resiliency of the elastomeric seal, and the extent to which it ispre-stressed (i.e., the extent to which the diameters of the upper andlower sealing rings are smaller than the diameters of the parts theyseal against), will depend on the predetermined pressure threshold thatis acceptable in a particular device.

In one example, the bellows seal is formed of a liquid silicone rubber(LSR) having a hardness of about 50 Shore A and a pre-stress of about 15to 40%, and is constructed to vent when the internal pressure exceeds0.3 bar. The geometry of this seal is shown in detail in FIG. 1B.

If desired, the bellows seal may be replaced by a seal having a singlesealing ring, rather than two sealing rings as described above. Forexample, the upper sealing ring 28 may be omitted.

The appliance may include an opening that does not have an actuatorbutton extending therethrough. For example, as shown in FIGS. 2-2B, thehousing 12 may include a groove 50 in which a vent aperture 52 isrecessed. A ring-shaped sealing element 54, e.g., an elastomeric gasket,is positioned in the groove 50 to seal aperture 52. The sealing elementis pre-stressed to seal it against the surface of groove 50.Pre-stressing is generally achieved by stretching the sealing element 54onto the groove; i.e., the diameter of the sealing element is slightlysmaller than that of the housing in the groove. It is generallynecessary that the material of the sealing element be sufficientlyflexible so that the sealing element can be stretched over thelarger-diameter areas of the housing when assembling it into the groove.

As shown in FIG. 2B, when battery B outgases, the increased internalpressure within housing 12 will slightly stretch the sealing element 54,forcing it away from the surface of the groove in the area of theaperture 52. This will allow the gas to vent around the sealing element54, as indicated by the arrows in FIG. 2B. As discussed above, ventingis so brief, and the extent to which the seal is displaced is so small,that it is very unlikely that water will enter the device duringventing.

In one example, sealing element 54 is formed of an elastomercommercially available under the tradename VITON, having a hardness ofabout 70 Shore A and a pre-stress of about 10 to 20% and beingcontructed to vent when the internal pressure exceeds 0.3 bar.

Referring now to FIGS. 3 and 3A, in some cases a small raised island 56may be provided around aperture 52 in groove 50. This raised island willtend to concentrate the pre-stress force of the gasket around theperimeter of aperture 52, increasing the sealing force so that, for agiven sealing ring design, a higher internal pressure will be requiredto break the seal. This is particularly helpful for think sealing rings.

In some cases, the battery may be contained in a carrier within thehousing. For example, as shown in FIGS. 4-4A the battery B may becontained in a carrier 60 having a groove 62, a venting aperture 64within the groove, and a ring-shaped sealing element 66 sealing theaperture, similar to the embodiment discussed above. It is importantthat, when gas exits the venting aperture 64, it exits the housing,rather than becoming trapped in the interior of the housing. Thus, thehousing includes a venting aperture 68, disposed relatively close to theventing aperture 64. If desired, the venting aperture 68 may be a seamline along which two parts of the housing may be separated from eachother, for example the main body of the housing and the batterycompartment cover. To prevent ingress of gas from the aperture 64 orwater from the aperture 68 into the interior of the housing, a seal 70is provided between the inner wall 72 of housing 12 and the outer wall74 of carrier 60 on either side of the apertures. The seal may be in theform of a pair of elastomeric o-rings, as shown, or any other suitabletype of seal. Seal 70 is designed to remain unbreakable at anyforeseeable pressure within the area between walls 72 and 74, preventingany leakage from this area into the housing. The gas flow path duringventing is first out through aperture 64 and then out through aperture68, as shown in FIG. 4A. In this embodiment, the sealing member 66 maybe visually hidden and protected by one part of the housing (e.g., themain housing body, shown on the right hand side in FIG. 4). The carrier60 may be permanently locked and sealed to the main housing body by oneof the o-rings, so that the sealing member 66 is shielded by the mainhousing body, while the battery compartment cover can be removed toallow replacement of the battery.

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention. Forexample, the venting aperture and sealing member may be provided inother areas of the housing and may have different relative geometries.As but one example, the circumference of the groove discussed above maybe generally elliptical. Moreover, while razors and toothbrushes havebeen mentioned above, the seals discussed herein may be used in any typeof water-tight appliance, for example flashlights, battery powered scrubbrushes, cameras and the like. Accordingly, other embodiments are withinthe scope of the following claims.

1. A water-tight, battery powered appliance comprising: a housing,having a generally hollow interior and an aperture through which gas canbe vented from the interior; and a seal, positioned to normally coverthe aperture, the seal being configured to flex in response to pressurewithin the hollow interior and move away from the aperture when apredetermined pressure is exceeded.
 2. The appliance of claim 1 furthercomprising a razor cartridge mounted on the housing.
 3. The appliance ofclaim 1 further comprising a toothbrush head mounted on the housing. 4.The appliance of claim 1 further comprising an actuator extending fromthe aperture.
 5. The appliance of claim 4 wherein the seal surrounds astem portion of the actuator.
 6. The appliance of claim 1 wherein theseal comprises a bellows-type seal.
 7. The appliance of claim 1 whereinthe seal comprises an elastomeric member.
 8. The appliance of claim 1wherein the predetermined pressure is between about 0.1 bar and 2 bar.9. The appliance of claim 1 wherein the aperture is positioned within acircumferential groove in an outer surface of the housing.
 10. Theappliance of claim 9 wherein the seal comprises a ring-shaped elementpositioned within the groove to cover the aperture.
 11. The appliance ofclaim 10 wherein the ring-shaped element comprises an elastomericgasket.
 12. The appliance of claim 10 wherein the ring-shaped element ispre-stressed to hold the ring-shaped element taut against the outersurface of the housing.
 13. A water-tight, battery powered appliancecomprising: a housing, having a generally hollow interior defining aninner wall, the housing having an aperture through which gas can bevented; a carrier, disposed within the housing and configured to hold abattery, the carrier having an aperture through which gas can be vented;a first seal, positioned between the carrier and the inner wall of thehousing, allowing fluid communication between the aperture in thehousing and the aperture in the carrier, but sealing against passage offluid past the first seal into the housing; and a second seal,positioned to normally cover the aperture in the carrier, the seal beingconfigured to flex in response to pressure within the hollow interiorand move away from the aperture when a predetermined pressure isexceeded.
 14. The appliance of claim 13 further comprising a razorcartridge mounted on the housing.
 15. The appliance of claim 13 furthercomprising a toothbrush head mounted on the housing.
 16. The applianceof claim 13 wherein the first and second seals each comprise anelastomeric member.
 17. The appliance of claim 13 wherein the housingand carrier are both generally cylindrical, and the first seal comprisesa pair of ring-shaped gaskets, positioned one on each side of theapertures in the carrier and housing to isolate the apertures from therest of the housing.
 18. The appliance of claim 13 wherein thepredetermined pressure is between about 0.1 bar and 2 bar.
 19. Theappliance of claim 13 wherein the aperture in the carrier is positionedwithin a circumferential groove in an outer surface of the carrier. 20.The appliance of claim 19 wherein the second seal comprises aring-shaped element positioned within the groove to cover the aperture.21. The appliance of claim 20 wherein the ring-shaped element comprisesan elastomeric gasket.
 22. The appliance of claim 20 wherein thering-shaped element is pre-stressed to hold the ring-shaped element tautagainst the outer surface of the housing.